BCM,DEM,ECM offline

[npc]

Hi Everyone, first-time post but have learnt a lot from you folks.
I need help to troubleshoot CANBUS communication issue on a 08 XC90 3.2:
Got ABS/Anti-skid service required message, and corresponding warning lights are on. After the vehicle restart, the message and warning lights disappear within one minute and then come back in a few minutes. AWD and ABS not working but otherwise drives fine.
Tried to scan in VIDA and found BCM, DEM and ECM offline.

20210701_VIDA_1.PNG (8.12 KiB) Viewed 1596 times

First thought was DEM as the fuse burnt twice during the winter so removed it from the network by unplugging the socket.
VIDA network still the same as above, now with CEM-1A64 code. Re-connect the DEM then the CEM-1A64 was gone. No other code pop up.
Checked resistance at the OBDII socket between CAN high and low, it's 61 ohm. Ground line 1.2 ohm to chassis ground terminal. No short-circuit to supply voltage nor open-circuit detected. Visually checked the cables and sockets on DEM, REM and ECM, seem to be fine. Also checked fuse 15 on CEM to confirm it got the power (~14V).
Got stuck here and need help with further troubleshooting. Any suggestion is appreciated!

[Masscomguru]

What are the actual codes? If you go to the delivery tab in VIDA , it will show you.

[npc]

Thank you for your reply.
This is the strange part. The delivery tab says no fault found however you can see those modules were grey out.

20210705_VIDA_1.PNG (13.43 KiB) Viewed 1575 times

If I disconnect the DEM, then I get the CEM-1A64.

20210705_VIDA_2.png (30.44 KiB) Viewed 1575 times

CEM-1A64 disappers when I reconnect the DEM.
My guess is that CEM can't talk with DEM,BCM, ECM and TCM so won't be able to retrieve codes from them? But in that case, I should see some code related to communication issues?
Also, if the TCM is really offline, I guess the car won't be driveable? But it drives okay.
This really puzzles me.

[Masscomguru]

There are some pointers here.
viewtopic.php?t=91070

[npc]

Thank you Masscomguru for your suggestions!
I went through the post you mentioned. Seems that's not my case.
For the green ones, I can right-click and see the parameters etc.
However for DEM, BCM and ECM, when I right-click I couldn't see anything.
In the network tab, these three show as "not responding" while the TCM is grey "not present".
Tha's why I doubt it's a communication issue.
Now I suspect it's the BCM. Noticed the brake booster vacuum pump has a leak. Ordered the repair kit and plan to repair it during the weekend. Will take a look at BCM while taking off the pump.
Any chance the pump can mess up with BCM communication?